A gas turbine engine installed as an aircraft engine comprises a compressor compressing ambient air, a combustor burning fuel together with the compressed air and a turbine for driving the compressor. The expanding combustion gases drive the turbine and also result in thrust used for propelling the aircraft.
Air breathing machines like jet engines consume large quantities of air. Air contains foreign particles in form of aerosols or larger particles which then enters the engine with the air stream. The majority of the particles will follow the gas path through the engine and exit with the exhaust gases. However, there are particles with properties of sticking on to components in the engine's gas path changing the aerodynamic properties of the engine and more particularly reducing engine performance. Typical contaminants found in the aviation environment are pollen, insects, engine exhaust, leaking engine oil, hydrocarbons coming from industrial activities, salt coming from nearby sea, chemicals coming from aircraft de-icing and airport ground material such as dust.
The contaminants sticking on to components in the engine gas path cause fouling of the engine. The consequence of gas path fouling is an engine operating less efficient. With the reduction in efficiency follows that the engine is less economic to operate and has higher emissions. Fouling will result in more fuel having to be burnt for achieving the same thrust as for the clean engine. Further, an environmental drawback is found with the higher fuel consumption in form of increased carbon dioxide emissions. In addition, more fuel being burnt results in higher temperatures in the engine's combustor. With this follows high temperature exposure to engine hot section components. The higher temperature exposures will shorten the life time of the engine. The higher firing temperature results in increased formation of NOx which is yet another environmental drawback. In summary, the operator of a fouled engine suffers from reduced engine lifetime, unfavourable operating economics and higher emissions. The airline operators have therefore a strong incentive keeping the engine clean.
It has been found that the only reasonable way to combat fouling is to wash the engine. Washing can be practised by directing a water jet from a garden hose towards the engine inlet. However, this method has limited success due to the simple nature of the process. An alternative method is pumping the wash liquid through a manifold with special nozzles directed towards the engine inlet face. The manifold would be temporarily installed on the engine cowl or on the engine shaft bullet during the wash operation. Simultaneously with spraying the washing liquid towards the engine inlet, the engine shaft is cranked by the use of its starter motor. The shaft rotation enhances the wash result by the mechanical movements. The shaft rotation allows the wash liquid to move over greater surface area as well as enhancing liquid penetration into the interior of the engine. The method is proven successful on most gas turbine jet engines types such as turbojets, turboprop, turboshaft and mixed or un-mixed turbofan engines.
A proper wash operation of a gas turbine engine can be confirmed by an observation that the wash liquid exits the engine at the engine outlet. At the engine outlet the wash liquid has become a waste liquid. The waste liquid may leave the engine outlet as a stream of liquid pouring to the ground. Alternatively may the waste liquid be carried with the air stream as fine droplets where the air stream is the result of the rotation of the engine shaft. This air borne liquid can be carried a significant distance before falling to the ground. It is shown from actual wash operations that waste liquid will be spread on a large surface area, typically more than 20 meters downstream of the engine outlet. It is not desired to spread waste liquid on the ground. It is the purpose of this invention to provide a method and apparatus to collect the waste liquid exiting the engine.
The waste liquid exiting the engine at washing consists of the wash liquid entering the engine together with released fouling material, combustion solids, compressor and turbine coating material, and oil and fat products. This waste liquid may be hazardous. As an example, analysis of water collected from actual turbine engine washing operations showed to contain cadmium. The cadmium comes from compressor blade coating material released during washing operation. Cadmium is environmentally very sensitive and can not be allowed to be disposed to the effluent. This waste liquid would have to undergo treatment for separation of hazardous components before being disposed in a sewer.
Gas turbine aircraft engines can be of different types such as turbojets, turboprop, turbo-shaft and mixed or un-mixed turbofan engines. These engines cover a large performance range and may comprise of different design details by different manufactures. Aircrafts types for a defined service may be offered from different aircraft manufacturers thus the design of the aircraft and its engines may vary. Further, the aircraft manufacturer may offer different engine options for the same aircraft type. The large combined possibility of engines on aircraft types and from different aircraft manufacturers result in a practical problem in designing a system for collecting and treating of waste wash liquid that is generally applicable to most winged aircraft. U.S. Pat. No. 5,899,217 to Testman, Jr. discloses an engine wash recovery system that is limited to small and particularly turboprop engines as the container used in the invention is not applicable to the air flows emanating from e.g. large turbo-fan engines.
Collecting waste water from engine washing may be accomplished by hanging canvas like collectors under the engine nacelle. However, any operation resulting in anything being hooked on to an engine has the disadvantage that it may be subject to engine damage